Admission control (AC) is a well-known and widely used radio resource management (RMM) function in a wide range of wireless access networks, including the Global Standard for Mobile (GSM) communications, the Generalized Packet Radio Service (GPRS), the Enhanced Data for GSM Evolution (EDGE), the wide-band code division multiple access (WCDMA) and the evolved Universal Terrestrial Radio Access (E-UTRA) wireless access networks. In general, admission control has the task to admit or reject a service request based on the available resources at the time of the service request and the resources that are needed to ensure proper quality for the particular service. For example, for WCDMA networks, admission control takes into account multi-cell radio resources rather than basing the admission control on the state of a single radio cell.
The capacity of wireless networks that include multiple radio access technologies (RATs) is a closely related and well-studied area. Multi-RAT networks are often characterized by an associated capacity region that jointly characterizes the number of different services that can be accommodated by the multi-RAT system.
Load balancing is a radio resource management (RRM) technique that is often used in multi-RAT networks. The purpose of load balancing is to assign or re-assign radio access technologies to in-progress sessions such that the overall radio resources are well utilized and thereby the overall capacity of the multi-RAT system is maximized under some quality of service or other constraint(s).
A well-known trade off in wireless networks, which is closely related to admission control, occurs between the blocking of newly arriving service requests and the dropping of on-going services. This trade off can be expressed as, the higher the number of in-progress sessions there is, there is an increased likelihood that some services need to be dropped due to insufficient resources or outages. At an extreme case, systems without any admission control are feasible as long as it is acceptable that certain sessions might need to be terminated prematurely in order to ensure system stability and maintain some service quality for non-dropped sessions.
The 3rd Generation Partnership Project (3GPP) is currently finalizing Release 8 of the Long Term Evolution (LTE) standards suite. LTE networks are expected to be deployed in the coming years by incumbent as well as green-field operators. As such, it is expected that LTE systems will often be deployed as part of an operating multi-access infrastructure. In such situations, the LTE radio access equipments will typically be integrated into operating with GSM/GPRS/EDGE/WCDMA systems.
There are two possible arrangements according to which a LTE base station can be deployed in conjunction with other RATs: co-located base stations and base stations with mixed technologies. With co-located base stations, LTE system requirements are co-located with the equipments of other RATs, possibly sharing some parts of the existing site infrastructure including power supply, transport networks, cellular tower, etc. In this type of deployment scenario, the set of equipment of each RAT is independent, although there can be some coordination on the level of various protocol layers.
With base stations having mixed technologies, the radio equipment used by the base stations are commonly used by all RATs (e.g., LTE, UTRAN, GSM, etc.). It might also be possible to share the base band processing part of the equipment. However, the higher layers operate independently. The primary benefit of a mixed technology base station is that it is cost efficient due to the use of only a single radio part. This quasi-integrated solution also makes the overall base station more compact and power efficient thereby also reducing the operating cost of network and site maintenance. Presently, the mixed technology base station is undergoing a rudimentary phase of standardization in various standardization bodies, which include GERAN and 3GPP RAN4.